Knife sharpening device



Feb. 10, 1948. E. w. ARK ETAL KNIFE SHARPENING DEVICE Filed Nov. 10; 1944 INVENTORS. awe w. M.

Patented Feb. 10, 1948 UNITED STAT ES PATENT OFFICE KNIFE SHARPENINGDEVICE Earl Clark andIGaI-IL. Clark, Warren, Ohio Application November 10, 1944, Serial No. :62.828

8 Claims.

1 This invention relates to an apparatus ordevice for sharpening knives and-more particularly to the resharpening of knives which have been dulled by ordinary usage. More specifically the apparatus described herein is applicable to the resharpening of household or kitchen knives which may have straight or'curvedor a combination of straight and curved cutting edges.

Accordingly it is an object of the present invention to provide an improved device which will resharpen the cutting edge of a knife at an exact predetermined angle, and in which the Wearing away of the sharpening stone will not materially alter this selected angle. Further, since in subsequent resharpening-the knife blade is held at the same angle with reference to the sharpening stone at which it was previously resharpened, it. is necessaryto remove only a minimum amount of metal in order torestore the cutting edge to its original condition. Thus the quality of the cutting edge is-maintained throughof can produce as substantially as good" a cutting edge as can a professional or experienced knife grinder.

The features of construction and method of operating by whichthe above and other desirable objects of this invention are obtained are hereinafter described in conjunction with the accompanying drawing hereby madea part of the specification, and wherein:

Fig. 1 is a plan view of the resharpening device showing the knife held in position ready for sharpening;

Fig. 2 is aside elevation of the device with the knife clamped in position for sharpening, the knife being shown in cross-section;

Fig. 3 is. a fragmentary end elevation of the device showing the knif'ein position for sharpen ing' the straight portion .of'its cutting edge;

Fig. 4. is a fragmentary endv elevation of-the device showing theknife imposition fcr'sharpen ing the curved portion of its cutting edge; and

Fig. 5 is a fragmentary view showing the clampin jaws of the knife holder.

Similar numerals refer to similar parts throughout the various figuresof the drawing.

Attention isdirected to-Figs. 1, 2, 3 and 4 wherein the base I supports thecutting stone 2 and to which pivot pin 3 is attached. Arm 4 is pivotally mountedon pivot pin 3 at one end and at the other end, inconjunction with hinge half I and pin 8, forms a hinge. Sleeve 5 supports arm 4- at the properheight. Nut 6 holds 4 in place on pivot pin 3 and permits the device to be readily dismantled. Parallel motion links 9 are pivotally mounted on hinge half I at one end and likewise on hinge half ID at the other end by means of shouldered rivets ll. Hinge pin [2 in conjunction with hinge halves l0 and [3 form a second hinge. On: hinge half l3 bracket I4 is pivotally mounted by means of shouldered rivet l5. Bracket l4: carries pivot pin I8 upon which knife clamps l6 and ll are pivotally mounted.

Reinforcing angle l9is fastened to clamping jaw l1 andisalsopivotally mounted on pin is. Reinforcihg. angle laisthreadedto receive screw 20 which has a ball end 'ZUa on one-end and a knurled wheel 20b on. the other end. When screw 20 is forced toward pivot pin 18' clamping jaws I6 and I! are forced together and securely clamp the knifeblade 21 as shown in Fig. 2.

Bracket I4 is. provided with a curved slot I 4a whose: center of curvature: coincides with that of: pin l8. shouldered-screw 22 engages slot Ma and is attachedito-reinforcing angle l9. Pin 22 in conjunction with slot Mwpermitsknife 2! to be swiveledabcut pin [8 from the angular position shown by full lines to. the angular position prevented" from being brought into a position wherein they would-form anangle of degrees.

In-Flg. 5, which shows the clamps I6 and I! engaging the knife blade 21, thefclamping surface of clamp I6 is-curved so that it will bear on the knife blade at one point only. This is essential because knife: bladesare frequently tapered in thickness toward thepolnt. Thus, with the use of the constructionshown, firm clamping of the knife blade is readilyobtalned'. V

The procedurensed in resharpening knives 3 with the apparatus shown and described herein is as follows:

The clamping jaws l6 and II are loosened by backing 01f screw 20. The knife holder is then raised vertically, which vertical movement is permitted by parallel motion links 9. Knife blade 2| is then inserted between clamps I6 and I1. Screw 2i) and ball 20a is advanced toward hinge pin l8 thereby clamping the knife blade 2i, securely in the knife holder. The knife holder has been previously brought to the angular position shown by full lines and clamped in position by screw 22. The knife is then allowed to rest on the oil stone 2 and the operator grasps the knife by its handle.

The straight portion of the knife is sharpened by placing the knife in the position shown in Fig. 3 and imparting a rotary motion thereto.

The combination of the hinged arm 4 and the hinge portions 1, l and I3 and the hinged parallel motion links 9 permits absolute freedom of knife movement just as if one were sharpening a knife on an oil stone without the assistance of our apparatus. However, our apparatus, while permitting complete freedom of movement, holds the knife blade at the predetermined angle with respect to oil stone 2. The vertical movement provided by links 9 is essential to the success of the sharpening operation to accommodate knives of different widths and variations in the width of any given knife blade. We have determined experimentally that without this provision for vertical movement severe binding may occur between the knife blade and stone at certain portions of the sharpening stroke. The other face of the cutting edge on the knife blade may be sharpened in a similar manner by loosencan be sharpened on the flat surface of the oil stone but it is more conveniently sharpened on the curved portion 2a of stone 2 as shown in Fig. 4. The same rotary motion is used as when sharpening the straight portion of the blade. In both these sharpening operations the hinges comprising parts 3, 4, 8,1, 9, l0; l2, l3, l4 and I5 co-act to permit complete freedom of movement of the knife in vertical, horizontal or inclined positions as required to sharpen any part of the knife blade. In all of these sharpening operations the knife blade is maintained at a practically constant angle with the cutting surface ofoil stone 2. s

From the above it is evident that the knife sharpener described herein overcomes the greatest difilculty that is experienced when sharpening knives by hand, namely,'the practical impossibility, except for a thoroughly experienced and skillful operator, of maintaining the knife blade at the proper angle to'the oil stone face during the sharpening operation.

Further, the curved portion 2a on oil stone 2 makes possible the sharpening of a knife blade which has a concave cutting edge.

We claim:

1. In a device for sharpening knives classed as kitchen cutlery and the like, a sharpening surface, means for holding the knife blade at a predetermined angle with reference to said. sharpening surface, and guiding means associated with said holding means whereby said knife can be moved in any direction relative to said sharpening surface, said guiding means consisting of a plurality of hinge members, hinge pins and a plurality of parallel motion links wherein one of said hinge members engages a fixed hinge pin at one end and at the other end forms a hinge with a second hinge member, said parallel motion links connecting said second hinge member with a third hinge member, a fourth hinge member connecting with said third hinge member, and said knife holding means attached to said fourth hinge member.

2. In a device for sharpening knife and shear blades including: a base; an abrasive member mounted thereon; an upwardly extended portion on said base; an arm pivotally connected to the upwardly extending portion on said base; a second arm pivotally connected to the first named arm; a third arm pivotally connected to the second arm; a fourth arm pivotally connected to the third arm; one of said arms comprising a plurality of hinge members connected by a plurality of parallel motion links; a blade clamp pivotally mounted on the fourth arm; the pivotal movement of said arms relative to each other and to said abrasive member permitting said blade to be brought into and maintained in grinding contact with said abrasive member and moved freely thereover while maintaining a fixed angular relation between said blade and said abrasive member.

3. In a device for sharpening knife and shear blades: a base; an abrasive member mounted thereon; a supporting member projecting from said base; an arm pivotally connected to said supporting member; a second arm pivotally connected to the first named arm; a third arm pivotally connected tothe second arm; a fourth arm pivotally connected to the third arm; a blade clamp pivotally mounted on the fourth arm; a clamp to fix said blade clamp to said fourth arm in any desired position; a stop whereby the first and second arms are prevented from being brought into a relative position wherein they are parallel: the pivotal movement of said arms relative to each other and to said abrasive member permitting said blade to be brought into and maintained in grinding contact with said abrasive member and moved freely thereover while maintaining a substantially fixed angular relation between said blade and said abrasive mem ber.

4. In a device for sharpening knife and shear blades: a base; an abrasive member mounted on to said fourth arm in any desired posit-ion; said abrasive mem er having a convex abrasive sur face thereon: the pivotal movement'of said arms relative to each other and to said abrasive member permitting said blade to be brought into and maintained in grinding contact with said abrasive member and moved freely thereover while maintaining a substantially fixed angular relation between said blade and said abrasive member and wherein any concave portion in the knife blade cutting edge may be sharpened on said convex abrasive surface of said abrasive member.

5. In a device for sharpening knife and shear blades: a base; an abrasive member mounted on said base; a pivot member projecting from said base; a blade clamp to hold said blades; a clamp supporting arm with a pivot pin thereon to carry said clamp; a series of pivotally connected arms, one outermost end of said series of arms being pivotally connected to said pivot member and the other outermost end of said series of arms pivotally connected to said clamp supporting arm; said blade clamp comprising: two blade clamping members hingedly mounted on said pivot pin; a screw operated wedge member mounted on one of said blade clampin members and arranged to force the clampin jaws of said blade clamp into firm contact on said blades; a positioning clamp associated with one of said blade clamping members and said clamp supporting arm to clamp said blade clamping member to said clamp supporting arm in any desired position on said clamp supporting arm: the pivotal movement of said arms relative to each other and to said abrasive member permitting said blades to be brought into and maintained in grinding contact with said abrasive member and moved freely thereover while maintaining a substantially fixed angular relation between said blades and said abrasive member and wherein both sides of the cutting edges of said blades may be sharpened without removing said blade from said blade clamp.

6. The combination with a device for sharpening knife and shear blades of a blade clamp comprising: a plurality of blade clamping mem bers havin diverging extended portions; a supporting arm; a, pivot pin attached to said arm and upon which said blade clamping members are mounted; a, screw operated wedge member arranged to engage said diverging extended portions to clamp said members upon the blade; a curved slot in said supporting arm; and means co-operating with said slot to regulate and determine the angle of the clamp.

7. The combination with a device for sharpening knife blades of a blade clamp comprising: a plurality of blade clamping members having diverging extended portions; a supporting arm; a pivot pin attached to said arm and upon which said blade clamping members are mounted; a wedge member adapted to engage said diverging extended portions and to clamp said clamping members upon the blade to be sharpened; and a, pin upon which said supporting arm is mounted whereby said clamp and blade may be rocked in a plane angular to that of the blade.

8. The combination with a sharpening device for sharpening the blades of knives and shears of a blade clamping device comprising: a blade clamp supporting arm; a pivot on said supporting arm; a blade clam with clamping jaws hingedly mounted on said pivot; wedging means to force said clamping jaws into firm contact with said blades, the longitudinal axis of said wedging means being located substantially in the plane of the blade of said knives; and means associated with said supporting arm and said blade clamp to clamp said blade clamp firmly to said supporting arm in any desired angular position.

EARL W. CLARK. CARL L. CLARK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 751,077 Jacques Feb. 2. 1904 816,662 Jeffrey Apr. 3, 1906 828,853 Ives Aug. 14, 1906 1,200,605 Glckler Oct. 10, 1916 2,165,929 Lentz July 11, 1939 

